For common bacterial infections no evidence exists that stopping antibiotic treatment early increases a patient's risk of resistant infection, the experts said. The latest call for a change in advice to patients is published in an article in the BMJ. "If you use penicillin, use enough", Fleming warned.
"'Exactly as prescribed' is OK and at least it gives flexibility in the discussion between doctor and patient about when to stop - perhaps when [the patients] have been reviewed, or have a certain test result, or have been better for a certain period of time", Llewelyn told Live Science. "My thought is that this is a radical stance-although in some ways correct", says Lance Price, a microbiologist and director of the Antibiotic Resistance Action Center at The George Washington University.
"As more clinical evidence comes into play we will reflect that in our guidelines but we need to be sure we are not doing any harm", said Dr Tony Bartone, Vice President of the AMA.
Telling patients to stop taking antibiotics when they feel better may be preferable to instructing them to finish the course, according to a group of experts who argue that the rule long embedded in the minds of doctors and the public is wrong and should be overturned.
Antibiotics are vital to modern medicine but overuse has contributed to antibiotic resistance, now considered a global threat to human health.
Here lies the problem - a course of antibiotics won't kill all of those microbes.
Numerous bacteria that are prone to causing risky antibiotic-resistant infections, such as Staph aureus and E coli, live on the body harmlessly without causing a problem most of the time. "The idea is deeply embedded, and both doctors and patients now regard failure to complete a course of antibiotics as irresponsible behavior", they wrote.
The scientist responsible for identifying penicillin as an antibiotic compound in the first place, Alexander Fleming, had long realised bacteria could become acclimatised to the substance's toxicity. This also means that longer the duration of the antibiotic use, longer the time the harmless bacteria in the gut gets to develop resistance and pass it on to the other strains and species of bacteria.
They said in the article: 'The fallacious belief that antibiotic courses should always be completed to minimise resistance is likely to be an important barrier to reducing unnecessary antibiotic use in clinical practice and to developing evidence to guide optimal antibiotic use.
"Outside hospital, where repeated testing may not be feasible, patients might be best advised to stop treatment when they feel better, in direct contradiction of WHO (World Health Organisation) advice". "Therefore, the overall message to conserve precious antibiotics is simple and important".
But Professor Stokes-Lampard said: 'Recommended courses of antibiotics are not random - they are tailored to individual conditions and, in many cases, courses are quite short.
England's chief medical officer Dame Sally Davies has warned that 50,000 people die each year in Europe and the United States from infections that have developed resistance against antibiotics.
Public Health England said patients should continue to follow their doctor's advice. "But we're not at that stage yet".
Lauri Hicks, director of the Office of Antibiotic Stewardship at the CDC, says she agrees that there are many unanswered questions about appropriate drug treatment courses.